1. Field of the Invention
The present invention relates to an apparatus and a method for Automatic Repeat reQuest (ARQ) in a wireless communication system. More particularly, the present invention relates to an apparatus and a method for generating an ARQ feedback message in the wireless communication system.
2. Description of the Related Art
Wireless communication systems can encounter data error due to channel conditions of radio resources carrying the data. Accordingly, the wireless communication systems control and restore the data error using an Automatic Repeat reQuest (ARQ) scheme to raise transmission reliability.
Using the ARQ scheme, a receiving end informs a transmitting end of success or failure of the reception of ARQ blocks received from the transmitting end. For example, when the ARQ blocks are received from the transmitting end without error, the receiving end sends ACK information to the transmitting end. In contrast, when the ARQ blocks are received from the transmitting end with error, the receiving end sends NACK information to the transmitting end. Herein, a series of operations for transmitting the success or failure of the reception of the ARQ blocks from the receiving end to the transmitting end is referred to as ARQ feedback.
In the ARQ feedback, the receiving end can utilize a cumulative ACK scheme, a selective ACK scheme, and a block sequence ACK scheme.
Using the block sequence ACK, the receiving end indicates the reception success or failure of the ARQ blocks received from the transmitting end using bitmap and length information.
Using the selective ACK scheme, the receiving end indicates the reception success or failure of the ARQ blocks received from the transmitting end using a bitmap constituted by assigning one bit to each ARQ block. The number of bits forming the bitmap is constant. Accordingly, when the receiving end conducts the ARQ feedback on the ARQ blocks smaller than the bits forming the bitmap in number, the receiving end and the transmitting end are likely to waste the bits excluding the bits indicative of the reception success or failure of the ARQ blocks in the bitmap.
Using the cumulative ACK scheme, the receiving end transmits to the transmitting end a sequence number of the ARQ block having the greatest sequence number among the ARQ blocks successfully received prior to the first erroneous ARQ block. For example, when the receiving end receives 10 ARQ blocks out of 12 ARQ blocks from the transmitting end and the fourth, fifth, seventh, and ninth ARQ blocks are corrupted, the receiving end sends the third ARQ block sequence number to the transmitting end.
However, when the first ARQ block received from the transmitting end is corrupted, the receiving end cannot send the ARQ block sequence number to the transmitting end. In addition, the receiving end cannot inform the transmitting end of ACK information of the ARQ blocks successfully received after the ARQ block sequence number sent to the transmitting end through the ARQ feedback.